TW202028835A - Display system, spatial light modulator system and method of forming display system - Google Patents

Abstract

A display system includes a spatial light modulator comprising a first substrate, a second substrate, and a liquid crystal layer between the first substrate and the second substrate. The spatial light modulator is characterized by a first retardation and a first phase retardation and has a first slow axis for light propagation. A voltage source is configured to apply a drive voltage to the spatial light modulator and the first retardation of the spatial light modulator is a function of the drive voltage. A retarder is positioned external to the spatial light modulator and is characterized by a second retardation and a second phase retardation. The retarder includes a second slow axis for light propagation. The second retardation has a value such that all illumination wavelengths in a set of illumination wavelengths are above or below a phase retardation value of 0.25. The set of illumination wavelengths includes at least one illumination wavelength in each of at least three different color spectrums.

Description

Display system, spatial light modulator system and method for forming display system

The present invention relates to Spatial Light Modulators (SLMs) (such as displays, liquid crystal displays (LCDs), liquid crystal microdisplays and liquid crystal spatial light modulators), which have independent operations Of pixels. More particularly, the present invention is directed to, for example, liquid crystal on silicon (liquid crystal on Silicon, LCoS) spatial light modulator or display spatial light modulator, which is applied to, but not limited to, projectors, head-up displays and, for example, head-mounted displays. Augmented Reality (AR), Mixed Reality (Mixed Reality) and Virtual Reality (Virtual Reality, VR) systems or devices that can be used as devices.

The liquid crystal spatial light modulator used in image capturing includes a type using ferroelectric liquid crystal (Ferroelectric Liquid Crystal) and a type using nematic liquid crystal (Nematic Liquid Crystal). The liquid crystal in the nematic type may have positive or negative dielectric anisotropy. The negative anisotropy type generally has higher contrast and is more suitable for projection and near-eye applications, such as AR and VR head-mounted devices. The spatial light modulator using liquid crystals with negative dielectric anisotropy uses an electro-optical mode (Electro-Optic) including a vertical alignment (Vertically Aligned Nematic, VAN) display mode and a twisted vertical alignment (Twisted Vertically Aligned Nematic, TVAN) display mode Mode). The twisted vertical alignment is described in US Patent Nos. 8,724,059 and 9,551,901, which are incorporated herein by reference.

The conventional optical design for viewing images from reflective liquid crystal spatial light modulators uses linear polarization in combination with wire-grid and MacNeille-cube polarizing beam splitters (PBS) to achieve high Contrast image. The disadvantage of using these types of polarizing beam splitters is that they occupy a relatively large volume, making it difficult to obtain streamlined and small product designs for AR and VR headsets. In addition, it is known that the use of a polarizing beam splitter will reduce image brightness, increase dynamic switching time, and increase the visibility of fringing field effects between adjacent pixels, especially in high-resolution spatial light modulator devices with short pixel pitch .

In order to overcome these deficiencies in the design of polarizing beam splitters, Kuan-Hsu Fan-Chiang, Shu-Hsia Chen, and Shin-Tson Wu reported in Applied Physics Letters, Volume 87, pp. 031110-1 to 031110-3 ( 2005)) describes an optical design that does not use a polarizing beam splitter. Its vertical alignment mode silicon-based liquid crystal spatial light modulator is exposed to broadband (Broadband) Circular Polarization (CP) (for example, instead of linear polarization) to overcome the long-standing problems of poor definition, low brightness and slow response time. The Chiang et al. publication does not introduce the electro-optic (EO) curve, nor does it give the illumination wavelength. In addition, the author only considered one direction of the circular polarizer.

Those skilled in the art can understand that broadband circularly polarized light can be produced by a linear polarizer having a polarization axis parallel to or perpendicular to the input axis of the broadband circular polarizer. Broadband circularly polarized light can also be generated by a linear polarizer with a polarization axis and a broadband quarter-wave plate (Quarter-Wave Plate, quarter-wave plate) slow axis set at an angle of ±45 degrees. Retarder of the refractive layer.

The phase retardation (φ) is a dimensionless quantity defined as the retardation length (Γ) divided by the illuminating wavelength λ (that is, φ = Γ/ λ). The retardation length Γ is the distance between the wavefront of the fast light (Fast Ray) and the wavefront of the slow light (Slow Ray) of the incident light after passing through the birefringent material.

The actual broadband quarter wave plates on the market are not ideal broadband quarter wave plates. For example, Teijin, Ltd. (Tokyo, Japan) supplies an FM-143 single-layer broadband quarter-wave plate. The wavelength distribution curve of the phase retardation of the FM-143 broadband quarter-wave plate is shown in Figure 2. It can be seen from Fig. 2 that when the wavelength is shorter than 555 nm, the phase retardation φ is greater than 0.25, but when the wavelength is longer than 555 nm, the phase retardation φ is less than 0.25. It will be seen that the deviation of the phase delay φ from 0.25 has a significant influence on the shape and contrast of the electro-optical curve.

Figures 3 and 4 illustrate the computer simulation of the present invention based on the method described in the Kuan-Hsu Fan-Chiang publication. The electro-optical curves for the red wavelength of 628nm, the green wavelength of 513nm and the blue wavelength of 453nm are plotted on the scale of linear and logarithmic pass rate (Throughput) respectively. The pass rate assumes that linearly polarized input light, an ideal polarizer with a transmittance of 1 and 0, and an ideal reflector with a reflectance of 1.

Here, the slow axis of the FM-143 broadband quarter-wave plate is oriented perpendicular to the slow axis of the vertical alignment mode spatial light modulator, which is parallel to the transparent first substrate and reflective of the spatial light modulator. The surface-contacting liquid crystal directors (Surface-Contacting liquid crystal directors) on the inner surfaces of the second substrates are aligned with the azimuth direction. The electro-optical curves of blue and green illumination in Fig. 4 on a logarithmic scale show a minimum pass rate near zero rather than zero under the driving voltage, while the electro-optical curves of red illumination are not shown.

In the electro-optical curve of blue and green illumination, the minimum pass rate near zero can be used to achieve a contrast greater than 2000. In particular, the value of the driving voltage is set to or close to a voltage close to the minimum value of the zero pass rate in the electro-optical curve of the blue and green illumination colors to reach the dark pixel. In order to realize bright pixels in the continuous spectrum of gray scale, the value of the driving voltage is set to be greater than the voltage to achieve the minimum value of near zero pass rate.

Temporarily refer to Figures 3 and 4, the horizontal axis is a continuous voltage from 0 to 10 volts. The pixel is in its darkest state at the voltage corresponding to the minimum pass rate close to zero. The gray level (Gray Level) is achieved by applying a voltage higher than the minimum voltage of the pass rate close to zero on the continuous area where the pass rate increases.

However, for red illumination, there is no near zero pass rate minimum in the electro-optical curve, and the contrast is only about 50. Contrast is defined as the ratio of the maximum pass rate divided by the minimum pass rate in the electro-optical curve.

Similarly, in Figures 5 and 6, the slow axis of the FM-143 broadband quarter-wave plate is oriented parallel to the slow axis of the vertical alignment mode spatial light modulator, where the electro-optic curve is shown in linear and Logarithmic scale. The pass rate of the red illumination curve in Fig. 6 on a logarithmic scale shows the minimum pass rate that is close to zero instead of zero under the driving voltage. In comparison, the blue and green photoelectric light curves do not show the minimum pass rate that is close to zero instead of zero under the driving voltage.

Through adopting the minimum pass rate in the red photoelectric light curve which is close to zero, the red contrast can exceed 2000. However, since the blue and green illuminating light does not have a pass rate minimum near zero in the electro-optical curve, the contrast of the blue and green illuminating light is unsatisfactorily lower than 110 and 210, respectively. Therefore, broadband quarter-wave plates are not suitable for applications that require high-quality and high-contrast full-color images (such as greater than 2000) for all illumination wavelengths.

The present invention maintains the advantages of the related technologies of the broadband quarter-wave plate method, including the advantages of small streamline design, short dynamic switching time, and almost invisible defects between pixels. In addition, the present invention overcomes the shortcomings of being unable to achieve high contrast requirements for all illumination wavelengths to achieve high contrast and full-color operation.

A system according to the present invention includes one or more retarders located outside a spatial light modulator (such as a reflective liquid crystal display or a reflective silicon-based liquid crystal display). The retarder generates a phase retardation φ greater than 0.25 for at least three wavelengths of illumination light used to form a color image (such as a full-color image). For example, the phase delay φ varies between 0.26 and 0.40 (including 0.26 and 0.40).

Alternatively, the retarder generates a phase retardation of less than 0.25 for at least three wavelengths of illumination light used to form a color image (such as a full-color image). For example, the phase delay varies between 0.10 and 0.24 (including 0.10 and 0.24).

In an embodiment of the present invention, the at least three illumination wavelengths include wavelengths corresponding to at least red, green, and blue, but may also include wavelengths of other colors such as yellow. For example, in an embodiment of the present invention, a retarder located outside the spatial light modulator or a combination of multiple retarders with different retardation lengths Γ produces a phase retardation greater than or less than 0.25 for all illumination wavelengths. φ. The illumination wavelength is used to obtain images, which include color images such as full-color images.

In an embodiment of the present invention, the phase retardation φ of the external retarder is greater than 0.25 for three different illumination wavelengths or colors. For example, in an embodiment of the present invention, different illumination wavelengths or colors correspond to red, green, and blue illumination wavelength bands (that is, the red wavelength band from 625 to 740 nanometers, and the wavelength from 500 to 565 nanometers. The illuminating wavelength of one wavelength in each of the green wavelength band of 450-485 nm and the blue wavelength band of 450-485 nanometers is used in a display such as a full-color display. Therefore, any light incident on the spatial light modulator at these wavelengths is not circularly polarized (for example, a phase retardation of 0.25 produces circularly polarized light). Those skilled in the art can understand that the illumination may also include yellow illumination, for example.

In one embodiment, the slow axis of the retarder is configured to be perpendicular or substantially perpendicular to the slow axis of a spatial light modulator, such as a vertical alignment or a twisted vertical alignment spatial light modulator. When zero volts is applied to the spatial light modulator, any residual value of the retardation length Γ of the spatial light modulator (such as introduced through the pretilt angle of the surface contact director in the liquid crystal spatial light modulator) is generated from the external retarder Subtracted from the delay length Γ. Here, the combined phase delay φ generated by the spatial light modulator and the retarder can be greater than 0.25, resulting in a non-zero pass rate. When the voltage applied to the spatial light modulator increases from zero, the delay length Γ of the spatial light modulator increases and is subtracted from the delay length Γ of the external retarder until the combined phase of the retarder and the spatial light modulator is reached Where the delay φ is equal to 0.25. Here, because the input polarization is rotated 90 degrees and is absorbed into the polarizer when reflected, the pass rate of this combination is zero. When the voltage is further increased, because the polarization rotation is no longer 90 degrees, the combined phase delay φ decreases from 0.25 as the pass rate increases.

Therefore, the pass rate is not zero at zero volts. At a voltage where the combined phase delay φ is 0.25, the pass rate drops to a minimum value close to zero, and then increases again at a higher voltage (e.g. higher than where the pass rate minimum value close to zero occurs) Voltage). Using this kind of electro-optical curve, the pixel driving voltage can be set to or close to the voltage at which the minimum pass rate in the electro-optical curve occurs to achieve dark pixels to achieve high pass rate and contrast (for example, greater than 2000) . The pixel drive voltage is increased to be higher than the voltage at which the pass rate minimum value near zero occurs to achieve a pixel gray scale with increased brightness. Contrast is defined as the ratio of the maximum pass rate in the electro-optical curve divided by the pass rate near zero minimum.

In another embodiment of the present invention, the phase retardation φ of the external retarder is less than 0.25 for the red, green, and blue wavelengths used in color displays (such as full-color displays), which represents incident on the silicon-based liquid crystal at these wavelengths. The light of the imaging unit is not circularly polarized (for example, a phase retardation of 0.25 produces circularly polarized light). In this embodiment, the slow axis of the retarder is configured to be parallel or parallel to the slow axis of the vertical alignment or twisted vertical alignment spatial light modulator. Under the application of zero volts, the residual retardation length Γ of the spatial light modulator introduced through the non-90-degree pretilt angle of the contact vector on the inner surface of the liquid crystal spatial light modulator is added to the retardation length of the external retarder. Here, the phase delay φ of the combination of the retarder and the spatial light modulator can be less than 0.25, resulting in a non-zero pass rate.

When the voltage applied to the spatial light modulator increases from zero, the delay length Γ of the spatial light modulator increases and the delay length Γ is added to the external retarder until it reaches the retarder and the space Where the combined phase delay φ of the optical modulator is equal to 0.25. Here, because the input polarization is rotated 90 degrees and is absorbed into the polarizer when reflected, the pass rate of this combination is zero. When the voltage is further increased, because the polarization rotation is no longer 90 degrees, the combined phase delay φ increases from 0.25 as the pass rate increases.

Therefore, the pass rate is not zero at zero volts. At a voltage where the combined phase delay φ is 0.25, the pass rate drops to a minimum value close to zero, and then increases again at a higher voltage. Using this kind of electro-optical curve, the pixel driving voltage can be set to or close to the voltage at which the minimum pass-through rate occurs in the electro-optical curve to achieve a high pass rate and a contrast greater than 2000.

The foregoing content has generally described some viewpoints and features of various embodiments, which should be interpreted as merely illustrating various potential applications of the present invention. Other beneficial results can be obtained by applying the disclosed information in different ways or by combining various viewpoints of the disclosed embodiments. Therefore, in addition to the scope defined by the scope of the patent application, by referring to the detailed description of the exemplary embodiments in conjunction with the drawings, other viewpoints and a more comprehensive understanding can be obtained.

Upon request, detailed embodiments are disclosed here. It must be understood that the disclosed embodiments are only examples of different and alternative forms. As used herein, the term "exemplary" is used broadly to refer to embodiments used as illustrations, samples, models, or patterns. The drawings are not necessarily drawn to scale, and certain features may be enlarged or reduced to show details of specific components. In other cases, the conventional components, systems, materials, or methods known to those skilled in the art are not described in detail to avoid making the content of the disclosure unclear. Therefore, the specific structure and function details disclosed in this article should not be construed as restrictive, but merely serve as a basis for the scope of patent application and as a representative basis for teaching ordinary knowledge in the field.

A system according to the present invention includes a retarder or a combination of retarders with a delay length Γ outside a spatial light modulator. The retarder or the combination of multiple retarders produces a phase retardation φ for all illumination wavelengths, which is greater than 0.25 for all illumination wavelengths or less than 0.25 for all illumination wavelengths. The light wavelength produces an image. For example, the image is a color image of a full-color image.

According to a system of the present invention, the spatial light modulator is, for example, a liquid crystal display of a reflective liquid crystal display.

FIG. 1 is a three-dimensional expanded schematic diagram of a display system 10 of a spatial light modulator according to the present invention. In an embodiment of the present invention, a spatial light modulator display system 10 includes a linear polarizer 100, an external retarder 200, and a reflective spatial light modulator 300. The red, green, and blue light 120 from a light source 400 can be guided to the pixels of the spatial light modulator display system 10, so that the light from one or more light sources can be used by at least a part of the pixels or all the pixels in a chronological manner. (For example, red light can be guided for a period of time, then green light can be guided for a period of time, and then blue light can be guided for a period of time). It is understood that other sequences of these colors can be used. The illumination light 120 is incident on the linear polarizer 100 and linearly polarized along the polarization axis 160 when passing through the linear polarizer 100.

This polarized light is then incident on the external retarder 200 whose slow axis 220 and the incident polarization direction or polarization axis 160 form a positive 45 degree angle (or substantially a positive 45 degree angle) on its plane. When passing through the retarder 200, the linearly polarized light is converted into elliptically polarized light instead of circularly polarized light, which is incident on the spatial light modulator 300. Circularly polarized light can be generated at an angle of 45 degrees and a phase retardation of 0.25. When the phase retardation is different from 0.25, the light will be elliptically polarized.

In one embodiment, the direction of the slow axis 340 on the plane of the spatial light modulator 300 is perpendicular (or substantially perpendicular) to the direction of the slow axis 220 of the external retarder 200, and the retarder has a wavelength of 0.25 or more for all illumination. A phase delay value of. In another embodiment, the direction of the slow axis 320 on the plane of the spatial light modulator 300 is parallel (or substantially parallel) to the direction of the slow axis 220 of the external retarder 200, and the retarder has a wavelength of 0.25 for all illumination. The following is a phase delay value.

The light 140 reflected from the spatial light modulator 300 passes through the external retarder 200 and the polarizer 100 again in the opposite direction, wherein the reflected light 180 emerges or exits from the polarizer 100 to be sensed by the eyes or other detectors. The intensity of the reflected light 180 depends on the voltage applied to each pixel of the spatial light modulator 300.

In detail, referring to FIG. 1, the spatial light modulator 300 includes a first alignment layer 302, a second alignment layer 304, and a liquid crystal located between the first alignment layer 302 and the second alignment layer 304 Material layer 306. The liquid crystal layer 306 includes a plurality of surface contact liquid crystal directors 308 on the first alignment layer 302 and the second alignment layer 304 and a non-surface contact liquid crystal director 309 on the main body of the liquid crystal layer 306. These surface contact directors 308 have, for example, an azimuth alignment direction according to the preset directions of the alignment layers 302 and 304. For example, these preset directions can be generated by materials deposited on the surface in an oblique direction, photosensitive materials on the surface irradiated with obliquely incident and polarized UV light, or unidirectionally rubbing the surface with a velvet-like cloth.

In the vertical alignment mode, the slow axis of the spatial light modulator 300 is parallel to the azimuth alignment direction of the surface contact liquid crystal director 308 (for example, 45 degrees). In the twisted vertical alignment mode, the slow axis of the spatial light modulator 300 is parallel to a line that divides the azimuth alignment direction (such as 0 degrees and 90 degrees) of the surface contact director 308 into two. Although the alignment layer 304 below the liquid crystal layer and the alignment layer 302 above each contain multiple surface contact liquid crystal directors, for ease of illustration, only one surface contact liquid crystal director is shown on the lower alignment layer 304 . Similarly, the main body of the liquid crystal layer 306 (such as the inner and middle portions except for the alignment layers 302 and 304) includes a plurality of directors over the entire thickness of the liquid crystal layer 306.

In addition, the surface contact liquid crystal director 308 has a characteristic of a pretilt angle 310. The pretilt angle 310 and the tilt angle 311 of the director 309 in the main body of the liquid crystal layer 306 determine the retardation length Γ of the spatial light modulator 300. According to an embodiment, the liquid crystal material 306 has negative dielectric anisotropy.

In addition, the spatial light modulator 300 includes a plurality of pixel electrodes, including a first electrode 312 and a second electrode 314 connected to a voltage source 316. The voltage source 316 is used to provide a voltage 317 to the electrodes 312 and 314 and thereby apply a voltage 317 to the liquid crystal layer 306 of each pixel of the second electrode 314 of the spatial light modulator 300. The voltage 317 of the liquid crystal layer 306 changes the tilt angle 311 of the director 309 in the main body of the liquid crystal layer 306 and thereby changes the overall retardation length Γ of the spatial light modulator 300. The voltage source 316 stores predetermined voltages or otherwise generates voltages related to the dark state and the bright state for each wavelength and pixel.

The spatial light modulator 300 further includes substrate layers 318 and 319 outside the electrodes 312 and 314. In detail, the substrate layer 318 is above the electrode 312, and the substrate layer 319 is below the electrode 314.

As described in further detail below, the electro-optical curve for each pixel can be operated through the driving voltage 317 related to a non-zero wavelength. The wavelength-dependent driving voltage 317 for the off state or the dark state of each wavelength is determined to be the voltage at which the electro-optical curve of the pass rate for the wavelength has a minimum value, which is close to zero (eg, less than 0.001). The on-state or bright-state, wavelength-dependent pixel drive voltage 317, which is higher than the off-state wavelength-dependent drive voltage, is applied to each pixel to increase the pixel throughput rate and provide gray levels.

Therefore, for a wavelength of the illumination light received from the light source 400, each pixel is controlled by an on-state wavelength-dependent drive voltage 317 or an off-state wavelength-dependent drive voltage 317 corresponding to the illumination wavelength.

It is obvious to those with skill or general knowledge that the polarizer 100, retarder 200, and spatial light modulator 300 (for example, the liquid crystal on silicon spatial light modulator shown in FIG. 1) are only in accordance with the present invention An example of an optical structure. For example, the slow axis 220 of the external retarder 200 may also form a negative 45 degree angle (or substantially a negative 45 degree angle) with the incident polarization direction or the polarization axis 160. In order to suppress the reflection from the front surface of the light source 400 that may cause or aggravate the contrast reduction, the polarizer 100 and the retarder 200 may be deposited with an anti-reflection coating 110 on one or both sides, and the spatial light modulator 300 may be on its substrate The top surface of layer 318 has an anti-reflective coating 110. Alternatively, two (or even all three) of the elements 100, 200, and 300 may be selectively coupled, for example, laminated together to reduce reflection at the interface.

For the sake of clarity, related optical elements such as lenses, mirrors, and mirrors are not shown in FIG. 1. According to an embodiment of the present invention, the red, green, and blue light sources 400 or light sources for full-color effects may include solid-state full-color diodes, light-emitting diodes (such as organic light-emitting diodes), solid-state lasers, and Gas lasers, and/or other sources of electromagnetic radiation such as light filtered from xenon, metal halide or tungsten halogen lamps. If the light source has been linearly polarized, such as some gas lasers and solid-state laser diodes, the polarizer in the incident light path can be omitted and a polarizer is retained in the reflection path. In such an embodiment (an embodiment in which the polarizer in the incident illumination path is omitted and the polarizer is retained in the reflection path), the polarization direction of the polarizer in the reflection path is parallel or substantially parallel to the polarization direction of the incident light source .

External retarder-delay selection

As described below, an external retarder with a selected delay can improve the performance of the spatial light modulator display system. The selection of the delay of the external retarder is discussed with reference to FIG. 7.

7 illustrates the wavelength distribution curve of the phase retardation φ of the 166nm external retarder 200 according to an embodiment of the present invention and the wavelength distribution curve of the phase retardation of the 107nm external retarder 200 according to another embodiment of the present invention.

The phase retardation φ is a dimensionless quantity characterized by the phase difference between the fast axis and the slow axis of light propagating through a birefringent layer or a combination of multiple birefringent layers, and it is defined as the retardation length Γ divided by Illumination wavelength λ (ie φ = Γ/ λ). The retardation length is the distance between the wavefront of the fast light and the wavefront of the slow light of the incident polarized light after passing through a birefringent material or a combination of multiple birefringent materials.

In one embodiment, the external retarder 200 has a retardation length Γ value, which is greater than a quarter of the longest wavelength of the electromagnetic radiation (such as light) transmitted to the spatial light modulator 300 (and, for example, less than or equal to 175 Nano). For example, if the longest illuminating wavelength is a red wavelength of 628 nm, the retardation length Γ of the external retarder 200 should be greater than 628/4 nm, that is, 157 nm at the wavelength. Taking this embodiment of the present invention as an example, it is shown in FIG. 7, where the delay length Γ completed by the external retarder 200 is 166 nm and the longest wavelength received by the external retarder 200 is a red light wavelength of 628 nm. For example, the value of the retardation length Γ is in the range of a quarter of the longest wavelength to 175 nm. In FIG. 7, for the external retarder 200 having a retardation length Γ value of 166 nm, the phase retardation φ is greater than 0.25 for each of the 453 nm wavelength, 513 nm wavelength, and 628 nm wavelength. Those skilled in the art can understand that the wavelength and the retardation length can be alternately selected so that the retardation length Γ of the external retarder 200 has a phase retardation φ which is greater than 0.25 for at least three wavelengths of different colors. For example, the delay length Γ of the external retarder 200 is selected according to a longest wavelength to be generated by the light source 400 described above.

In another embodiment, the external retarder 200 has a retardation length Γ value, which is less than a quarter of the shortest wavelength used for display illumination (and, for example, greater than or equal to 100 nanometers). For example, if the shortest illuminating light wavelength is a blue wavelength of 453 nanometers, the retardation length Γ of the external retarder 200 should be less than 453/4 nanometers, that is, 113.25 nanometers. Taking this as an example, it is shown in FIG. 7, where the retardation length completed by the external retarder 200 is 107 nm and the shortest wavelength is a blue light wavelength of 453 nm. For example, the retardation length Γ value is in the range of 100 nanometers to a quarter of the shortest wavelength. In FIG. 7, for the external retarder 200 having a retardation length Γ value of 107 nm, the phase retardation φ is less than 0.25 for each of the 453 nm wavelength, 513 nm wavelength, and 628 nm wavelength. Those skilled in the art can understand that the wavelength and the retardation length can be alternately selected so that the retardation length Γ of the external retarder 200 has a phase retardation φ which is less than 0.25 for at least three wavelengths of different colors. For example, the delay length Γ of the external retarder 200 is selected according to a shortest wavelength to be generated by the light source 400 described above.

Table 1 below lists the phase retardation φ of at least three wavelengths as an example of the embodiment of the present invention. For example, one embodiment of the present invention includes an external retarder 200 with a delay length Γ of 166 nm, and another embodiment includes an external retarder 200 with a delay length Γ of 107 nm. It should be noted that the phase retardation φ in the embodiment including an external retarder 200 having a retardation length Γ of 166 nm is greater than 0.25 for all three wavelengths λ, and when including a retardation length of 107 nm An embodiment of an external retarder 200 of Γ is less than 0.25 for all three wavelengths.

Table 1

To Γ = 166 nm Γ = 107nm λ φ Δφ Φ Δφ 453nm 0.367 0.117 0.236 -0.014 513nm 0.323 0.073 0.209 -0.041 628nm 0.264 0.014 0.171 -0.079

In the embodiment of the present invention listed in Table 1 above, the wavelengths of blue light, green light and red light are selected as 453 nm, 513 nm and 628 nm, respectively. It is obvious to those skilled or general knowledge that other wavelengths of blue, green and red light can also be used, and other colors such as but not limited to yellow can also be added to increase the color gamut of a full-color display.

The phase delay difference Δφ is the difference between the phase delay φ of the combination of the external retarder 200 and the phase delay φ of 0.25 (that is, the light is circularly polarized at a phase delay φ of 0.25). The phase delay difference Δφ is positive in the embodiment where the delay length Γ of the external retarder 200 is 166 nm, and is negative in the embodiment where the delay length Γ of the external retarder 200 is 107 nm. In an embodiment of the present invention, a spatial light modulator (e.g., a display) according to the present invention achieves a high contrast ratio of 2000 or more for all wavelengths, for example, three wavelengths, when the magnitude of the phase retardation difference Δφ ( That is, when |Δφ|) is equal to or greater than 0.01 for all three wavelengths, this value of |Δφ| realizes or ensures that the phase retardation is above 0.25 for all wavelengths of the external retarder 200 of 166 nm, or for 107 nm All wavelengths of the external retarder 200 are below 0.25.

The improved performance of the spatial light modulator display system-the minimum pass rate in the electro-optical curve

The use of an external retarder with a retardation selected as described above in a spatial light modulator display device improves the performance of the spatial light modulator display system, which can be viewed through the electro-optics of the spatial light modulator display system Curve to confirm. The electro-optical curve shows the throughput rate of the spatial light modulator display system 10 for a wavelength from the light source 400 as a function of the voltage applied by the voltage source 316. Contrast is defined as the ratio of the maximum pass rate of the electro-optical curve divided by the minimum pass rate of the electro-optical curve that is close to zero (for example, less than 0.001).

Simulation can be performed by commercial software packages, such as LCDBench Version 6.42 and Analyzer Version 6.60, both of which are available from Shintech, Tokyo, Japan. In an embodiment of the present invention, a cell gap of a spatial light modulator (that is, the distance between the surfaces of the first and second alignment layers 302 and 304 facing the liquid crystal layer 306 pixels) is 0.9 microns; The birefringence coefficient Δn is 0.2206 at 453 nm, 0.2016 at 513 nm, and 0.1859 at 628 nm; the pretilt angle is 84 degrees; the light is incident vertically; and the reflector and polarizer are ideal reflections And polarizer.

For all the simulations in the present invention, including the electro-optical curves drawn in Figures 3 to 6 for the prior art simulation, the gap of the silicon-based liquid crystal cell is 0.9 microns, and the liquid crystal birefringence coefficient Δn is 0.2206 at 453 nm. It is 0.2016 at 513nm and 0.1859 at 628nm. The pretilt angle (that is, the angle 310 formed by the surface contact director 308 of the liquid crystal layer 306 in the spatial light modulator 300 and the plane of the spatial light modulator 300) is measured from the plane of the spatial light modulator 300 as 84 degrees. These simulations were performed with normal incident light and assumed an ideal 100% reflector and an ideal polarizer 100. Those skilled in the art can understand that this is only used to represent a selected one of the multiple examples of the present invention. For example, in the embodiment of the present invention, the cell gap can be changed between 0.5 microns and 3.0 microns (including 0.5 microns and 3.0 microns) depending on the refractive index of the liquid crystal used; and the pretilt angle can be limited to 89 degrees to 75 degrees. Change between (including 89 degrees and 75 degrees).

8 and 9 are electro-optical curves plotted on linear and logarithmic scales with 453 nm blue wavelength, 513 nm green wavelength and 628 nm red wavelength simulated according to an embodiment of the present invention, wherein the external retarder 200 has 166 A delay length Γ of nanometers and its slow axis 220 are oriented perpendicular to the slow axis 340 of the vertical alignment mode spatial light modulator 300.

FIG. 9, which is a logarithmic scale, shows that an exemplary embodiment of the spatial light modulator display system 10 has a minimum pass rate of nearly zero in the electro-optical curve for all three colors of less than 0.00001. These minimum pass rates close to zero for the illumination color below 0.001 are achieved through the present invention. For example, the present invention uses the above-mentioned retarder 200 with a retardation length Γ of 166 nm, and it uses an external broadband four. There is no existing technical solution for a half-wave plate. (As shown in Figure 4 and Figure 6, it only shows that some pass rates have a minimum value below 0.001).

10 and FIG. 11 are the simulated electro-optical curves of the spatial light modulator display system 10 including an external retarder 200 with a retardation length Γ of 107 nm, drawn on linear and logarithmic scales according to an embodiment of the present invention. The slow axis 220 of the external retarder 200 is oriented parallel to the slow axis 320 of the vertical alignment mode spatial light modulator 300.

Fig. 11, which is a logarithmic scale, shows an example of the spatial light modulator display system 10 according to the present invention. For all three colors (i.e., red, blue, and green), the minimum value of the pass rate near zero in the electro-optical curve is Less than 0.00001. These near zero pass rate minimum values of 0.001 or less for all illumination colors are the characteristics of the present invention, and they do not exist in the prior art solution using an external broadband quarter-wave plate.

Figures 12 and 13 are simulated electro-optical curves drawn on linear and logarithmic scales according to an embodiment of the present invention, wherein the external retarder 200 has a retardation length Γ of 166 nm and its slow axis 220 is oriented perpendicular to a The slow axis 340 of the vertical alignment mode spatial light modulator 300 is twisted 90 degrees. For the computer simulation, the slow axis 340 of the twisted vertical alignment mode is parallel to the bisector of the azimuth alignment direction on the alignment layers 302 and 304 of the spatial light modulator 300.

Fig. 13, which is a logarithmic scale, shows that in the electro-optical curve, the minimum pass rate for all three colors near zero is less than 0.00014. These minimum pass rates for all illuminating colors are the characteristics of the present invention, and they do not exist in the prior art solution using an external broadband quarter-wave plate.

14 and 15 are simulated electro-optical curves drawn on linear and logarithmic scales according to an embodiment of the twisted vertical alignment of the present invention, where the external retarder 200 has a retardation length Γ of 107 nm and its slow axis 220 is oriented as Parallel to the slow axis 340 of the spatial light modulator 300 in a twisted vertical alignment mode.

Figure 15, which is a logarithmic scale, shows that the minimum pass rate for all three colors in the electro-optical curve is less than 0.0001. These minimum pass rates for all illuminating colors are the characteristics of the present invention, and they do not exist in the prior art solution using an external broadband quarter-wave plate.

Dark state and bright state drive voltage

In one embodiment, the liquid crystal display 10 can be operated through the driving voltage 317 to maintain the respective pixels of the liquid crystal display 10 in an off state for each light wavelength. In an electro-optical curve, the liquid crystal display 10 is in an off state when there is a voltage at which the pass rate minimum value is zero or close to zero for each illuminating wavelength.

The liquid crystal display 10 can also be operated and/or operated by a driving voltage 317 to maintain the respective pixels of the liquid crystal display 10 in an ON state for each light wavelength. When the voltage is above the OFF State voltage, the liquid crystal display is in an operating state.

In the embodiment of the present invention, the minimum pass rate in the electro-optical curve occurs at the voltage where the combined phase delay φ is 0.25. The combination of the retardation length of the external retarder and the retardation length of the spatial light modulator produces circular polarization at a voltage close to zero at the minimum pass rate. This was invented under different voltages for each illuminating wavelength. In contrast, the external retarder with selected retardation as described above produces elliptical polarization at the wavelength used to determine the selected retardation.

In the embodiment of FIG. 11 and FIG. 15 of the present invention, the retardation length Γ of the liquid crystal layer 306 is added to the retardation length Γ of the external retarder 200 to achieve a combined phase retardation φ of 0.25. In order to achieve a contrast greater than 2000 for a given color, a spatial light modulator such as a liquid crystal on silicon spatial light modulator according to the present invention is driven with a pixel driving voltage 317. The pixel driving voltage 317 of the silicon-based liquid crystal spatial light modulator according to the present invention is at or near the voltage at which the minimum pass rate in the electro-optical curve occurs, so as to realize a dark pixel (for example, a stopped state). ). In an embodiment of the present invention, the pixel driving voltage 317 is increased above the off-state voltage to achieve a pixel gray level with increased brightness.

In the embodiment of FIG. 9 and FIG. 13 of the present invention, the retardation length Γ of the liquid crystal layer 306 is subtracted from the retardation length Γ of the external retarder 200 to obtain a combined phase retardation φ of 0.25. In order to achieve a contrast greater than or equal to 2000 for a given color, the silicon-based liquid crystal display 10 is driven with a pixel driving voltage 317. The pixel driving voltage 317 is a voltage corresponding to or close to the voltage at which the minimum pass rate of the electro-optical performance of a spatial light modulator occurs near zero in the electro-optical curve to realize a dark pixel (that is, a stopped state). The pixel driving voltage 317 is increased above the off-state voltage to achieve an increased brightness of the pixel gray level (that is, an operating state).

External retarder with fixed phase delay

The above-described embodiment of the present invention includes an external retarder 200 with different retardation lengths Γ of 166 nm and 107 nm. For simulation, these retardation lengths Γ are assumed to be independent of the wavelength, which can be approximated by the retarder 200 made of polyvinyl alcohol. However, as shown in Figure 7, the phase retardation φ of these retarders is wavelength dependent. This is because the phase delay φ is given as φ = Γ/λ. Because the retardation length Γ is a constant value, the phase retardation φ is a function of wavelength.

16 and 17 are simulated electro-optical curves drawn on linear and logarithmic scales according to an embodiment of the present invention, in which the external retarder 200 has a fixed phase delay φ of 0.26 and its slow axis 220 is oriented perpendicular to the vertical alignment mode space The slow axis 340 of the optical modulator 300 is a logarithmic scale, Fig. 17 shows that in the electro-optical curve for all three colors, the minimum pass rate is less than 0.0001. In one embodiment, a contrast ratio greater than 2000 for a given color can be achieved by driving the spatial light modulator 300 with a pixel driving voltage 317. The pixel driving voltage 317 is set at or close to the voltage at which the minimum pass rate in the electro-optical curve occurs to realize a dark pixel. The pixel driving voltage 317 is increased above this value to achieve pixel gray levels with increased brightness.

Compare the electro-optical curve in FIG. 8 (the present invention uses an embodiment of a retarder 200 with a retardation length Γ of 166 nm) and the corresponding electro-optical curve in FIG. 16 (the present invention uses a phase delay φ fixed to 0.26 The retarder 200 slow axis 220 of the retarder 200 is perpendicular to the slow axis 340 of the spatial light modulator) shows that the electro-optical curves of blue and green wavelengths are steeper and the driving voltage 317 is higher than the electro-optical curve. The minimum value of zero is used to achieve a higher pass rate. An external retarder 200 with a fixed phase delay φ may be better than an external retarder with a delay length Γ, especially in the case where the driving voltage is limited to a lower value due to the pixel circuit design of the spatial light modulator 300 in.

Similarly, a simulation using an example of an embodiment of a retarder 200 with a phase delay φ fixed to 0.24 and whose slow axis 220 is oriented parallel to the slow axis 320 of the spatial light modulator shows that it is almost the same as in FIGS. 16 and 16 Figure 17 shows the electro-optical curve of the electro-optical curve.

The phase delay φ used in these examples does not have to be completely fixed to achieve a steep electro-optical curve with high throughput. According to the present invention, a retarder 200 with a phase delay almost fixed to 0.26 is, for example, S. Pancharatnam, Part I and Part II, in The Proceedings of the Indian Academy of Sciences, Vol. XLI, No. 4, Sec. A , pages 130-144, 1955 combines three external retarders with different retardation lengths Γ and orientation angles.

method

Referring to Figure 18, an exemplary method 500 according to an exemplary embodiment of the present invention is illustrated. According to a first step 510, a set of illumination wavelengths is determined. The group of illumination wavelengths includes at least one illumination wavelength in each of at least three different color spectra. For example, at least one illuminating wavelength is determined from each of a 625-740 nanometer red wavelength band, a 500-565 nanometer green wavelength band, and a 450-485 nanometer blue wavelength band.

According to a second step 520a, an external retarder with a delay is selected relative to a minimum delay. The retardation makes the phase retardation greater than 0.25 for each of the wavelengths of the illumination light. In detail, the minimum retardation is calculated as a quarter of the longest wavelength (such as the wavelength in the red band in the above example).

According to a third step 530a, the slow axis of the external retarder with the selected retardation is oriented relative to the slow axis of the spatial light modulator. The slow axis of the retarder is oriented perpendicular to the slow axis of the spatial light modulator.

As another way, according to a second step 520b after the first step 510, an external retarder with a delay is selected relative to a maximum delay. The retardation makes the phase retardation less than 0.25 for each of the wavelengths of the illumination light. In detail, the maximum retardation is calculated as a quarter of the shortest wavelength (such as the wavelength in the blue band in the above example).

According to a third step 530b, the slow axis of the external retarder with the selected retardation is oriented relative to the slow axis of the spatial light modulator. The slow axis of the retarder is oriented parallel to the slow axis of the spatial light modulator.

The above-mentioned embodiments are merely exemplary illustrations of implementations set forth in order to clearly understand the principle. Without departing from the scope of the patent application, changes, modifications and combinations can be made to the above-mentioned embodiments. All these changes, modifications and combinations are included in the scope of the present invention and the appended application patents herein.

10: Spatial light modulator display system 100: Linear polarizer 110: Anti-reflective coating 120: Illumination 140: Reflected Light 160: optical axis 180: reflected light 200: external retarder 220, 340, 320: slow axis 300: Reflective spatial light modulator 302: first alignment layer 304: second alignment layer 306: liquid crystal material layer, liquid crystal layer 308: Surface contact liquid crystal director 309: Non-surface contact liquid crystal director 310: pretilt angle 311: inclination 312: first electrode 314: second electrode 316: voltage source 317: Voltage 318: substrate layer 319: substrate layer 400: light source Γ: Delay length 500: display system formation method 510: first step 520a, 520b: second step 530a, 530b: third step

FIG. 1 is a three-dimensional expanded schematic diagram of the display system of the spatial light modulator according to the present invention. Fig. 2 shows the wavelength distribution curve of the phase retardation φ of the broadband quarter wave plate of the prior art. Figure 3 is a broadband quarter wave plate simulation of a 453nm blue light wavelength, 513 nm using a prior art broadband quarter wave plate of a spatial light modulator with a vertical alignment mode in which the slow axis of the retarder and the slow axis of the spatial light modulator are perpendicular to each other. The wavelength of green light at nanometers and the wavelength of red light at 628 nanometers are plotted on a linear scale electro-optic curve. Fig. 4 is a broadband quarter-wave plate simulation of a spatial light modulator with a vertical alignment mode in which the slow axis of the retarder and the slow axis of the spatial light modulator are perpendicular to each other using the prior art. The wavelength of green light at nanometers and the wavelength of red light at 628 nanometers are plotted on a logarithmic scale electro-optic curve. Fig. 5 is a broadband quarter-wave plate simulation of a 453nm blue light wavelength, 513 using a prior art broadband quarter-wave plate of a spatial light modulator in which the slow axis of the retarder and the slow axis of the spatial light modulator are parallel to each other with a vertical alignment mode. The wavelength of green light at nanometers and the wavelength of red light at 628 nanometers are plotted on a linear scale electro-optic curve. Fig. 6 is a broadband quarter-wave plate simulation of a spatial light modulator with a vertical alignment mode in which the slow axis of the retarder and the slow axis of the spatial light modulator are parallel to each other using the prior art to simulate 453 nm blue wavelength, 513 The wavelength of green light at nanometers and the wavelength of red light at 628 nanometers are plotted on a logarithmic scale electro-optic curve. FIG. 7 shows a wavelength distribution curve of the phase retardation of a 166 nm retarder according to an exemplary embodiment of the present invention and a wavelength distribution curve of the phase retardation of a 107 nm retarder according to an exemplary embodiment of the present invention. Fig. 8 is a plot of 453 nm blue light wavelength, 513 nm green light wavelength and 628 nm red light wavelength simulated by a spatial light modulator with a vertical alignment mode using a 166 nm retarder according to an exemplary embodiment of the present invention Electro-optical curve on a linear scale. Figure 9 is a plot of a 453nm blue wavelength, 513nm green wavelength and 628nm red wavelength simulated by a spatial light modulator with a vertical alignment mode using a 166nm retarder according to an exemplary embodiment of the present invention The electro-optical curve on a logarithmic scale. Figure 10 is a plot of 453nm blue wavelength, 513nm green wavelength and 628nm red wavelength simulated by a spatial light modulator with a vertical alignment mode using a 107nm retarder according to an exemplary embodiment of the present invention Electro-optical curve on a linear scale. Figure 11 is a plot of 453nm blue wavelength, 513nm green wavelength and 628nm red wavelength simulated by a spatial light modulator with a vertical alignment mode using a 107nm retarder according to an exemplary embodiment of the present invention The electro-optical curve on a logarithmic scale. Figure 12 is a simulation of 453nm blue wavelength, 513nm green wavelength and 628nm red using a 166nm retarder in a spatial light modulator with a 90-degree twist vertical alignment mode according to an exemplary embodiment of the present invention The light wavelength is plotted on the electro-optical curve on a linear scale. Figure 13 is a simulation of 453nm blue wavelength, 513nm green wavelength and 628nm using a 166nm retarder in a spatial light modulator with a 90-degree twist vertical alignment mode according to an exemplary embodiment of the present invention The wavelength of nanored light is plotted on a logarithmic scale electro-optic curve. Figure 14 is a simulation of 453nm blue wavelength, 513nm green wavelength and 628nm using a 107nm retarder in a spatial light modulator with a 90-degree twist vertical alignment mode according to an exemplary embodiment of the present invention The wavelength of nano red light is plotted on the electro-optic curve on a linear scale. 15 is a simulation of 453nm blue wavelength, 513nm green wavelength and 628nm using a 107nm retarder in a spatial light modulator with a 90-degree twist vertical alignment mode according to an exemplary embodiment of the present invention The wavelength of nanored light is plotted on a logarithmic scale electro-optic curve. Fig. 16 is a simulation of 453nm blue wavelength, 513nm green wavelength and 628nm using a retarder with a fixed phase delay φ of 0.26 in a spatial light modulator in a vertical alignment mode according to an exemplary embodiment of the present invention The wavelength of red light is plotted on the electro-optical curve on a linear scale. Figure 17 is a simulation of 453 nm blue wavelength, 513 nm green wavelength and 628 nm using a retarder with a fixed phase delay φ of 0.26 in a spatial light modulator in a vertical alignment mode according to an exemplary embodiment of the present invention The wavelength of red light is plotted on the electro-optic curve on a logarithmic scale. FIG. 18 is a flowchart illustrating an exemplary method of forming a display system according to an exemplary embodiment of the present invention.

10: Spatial light modulator display system

100: Linear polarizer

110: Anti-reflective coating

120: Illumination

140: Reflected Light

160: optical axis

180: reflected light

200: external retarder

220, 340, 320: slow axis

300: Reflective spatial light modulator

302: first alignment layer

304: second alignment layer

306: liquid crystal material layer, liquid crystal layer

308: Surface contact liquid crystal director

309: Non-surface contact liquid crystal director

310: pretilt angle

311: inclination

312: first electrode

314: second electrode

316: voltage source

317: Voltage

318: substrate layer

319: substrate layer

400: light source

Claims (22)

A display system that includes: A spatial light modulator includes a first substrate, a second substrate, and a liquid crystal layer located between the first substrate and the second substrate, wherein the spatial light modulator has a first retardation length and a first A feature of phase delay, wherein the spatial light modulator has a first slow axis for light propagation; and A retarder is located outside the spatial light modulator, wherein the retarder has the characteristics of a second delay length and a second phase delay, and the retarder includes a first retarder perpendicular to the first slow axis and used for light propagation Two slow axes, wherein the second retardation length has a value such that the retarder has a phase retardation value of 0.25 or more for all the illuminating wavelengths in a set of illuminating wavelengths, wherein the set of illuminating wavelengths includes each of at least three different color spectra At least one of the illuminating wavelengths. The display system according to claim 1, comprising a polarizer having a polarization axis, wherein the retarder is between the polarizer and the spatial light modulator, and wherein the second slow axis rotates relative to the polarization axis 45 degree. The display system according to claim 1, wherein the second delay length has a value greater than a quarter of a longest illuminating wavelength of the group of illuminating wavelengths. The display system according to claim 1, comprising a voltage source for applying a driving voltage to the spatial light modulator, wherein the first delay length of the spatial light modulator is a function of the driving voltage Wherein, for each of the illumination wavelengths in the set of illumination wavelengths, the driving voltage for an off state is set to an off state driving voltage, wherein the first phase delay and the second phase delay are combined The value of is equal to or close to 0.25 to make a contrast greater than 2000. The display system according to claim 4, wherein at an on-state drive voltage greater than the off-state drive voltage, there is a maximum pass rate of each illuminating wavelength in a respective electro-optical curve. The display system according to claim 1, wherein the spatial light modulator is used for receiving incident light and outputting an image, wherein the image includes at least three different colors corresponding to each of the illumination wavelengths in the group of illumination wavelengths, and wherein each A contrast ratio of the three different colors is greater than 2000. The display system according to claim 1, wherein the at least three different color spectra include red, green and blue spectra. The display system according to claim 1, wherein the retarder generates a phase retardation φ for all illumination wavelengths, which has a value in the range of 0.26 to 0.40 for all illumination wavelengths. The display system according to claim 1, wherein the display system is a silicon-based liquid crystal display that operates in at least one of a vertical alignment mode and a twisted vertical alignment mode. The display system according to claim 1, wherein the delay device includes a plurality of delay devices. A display system that includes: A spatial light modulator includes a first substrate, a second substrate, and a liquid crystal layer located between the first substrate and the second substrate, wherein the spatial light modulator has a first retardation length and a first A feature of phase delay, wherein the spatial light modulator has a first slow axis for light propagation; and A retarder is located outside the spatial light modulator, wherein the retarder has the characteristics of a second delay length and a second phase delay, and the retarder includes a first slow axis parallel to the first slow axis and used for light propagation. Two slow axes, where the second retardation length has a value such that the retarder has a phase retardation value of less than 0.25 for all illuminating wavelengths in a set of illuminating wavelengths, wherein the set of illuminating wavelengths includes each of at least three different color spectra At least one of the illuminating wavelengths. The display system of claim 11, comprising a polarizer having a polarization axis, wherein the retarder is between the polarizer and the spatial light modulator, and the second slow axis rotates relative to the polarization axis 45 degree. The display system according to claim 11, wherein the second delay length has a value which is less than a quarter of a shortest illuminating wavelength of the group of illuminating wavelengths. The display system of claim 11, comprising a voltage source for applying a driving voltage to the spatial light modulator, wherein the first delay length of the spatial light modulator is a function of the driving voltage Wherein, for each of the illumination wavelengths in the set of illumination wavelengths, the driving voltage for an off state is set to an off state driving voltage, wherein the first phase delay and the second phase delay are combined The value of is equal to or close to 0.25 to make a contrast greater than 2000. The display system according to claim 14, wherein at each off-state driving voltage, for each light wavelength, there is a minimum value of zero or close to zero in an electro-optical curve. The display system according to claim 11, wherein the spatial light modulator is used to receive incident light and output an image, wherein the image includes at least three different colors corresponding to each of the illumination wavelengths in the group of illumination wavelengths, and wherein each A contrast ratio of the three different colors is greater than 2000. The display system according to claim 11, wherein the at least three different color spectra include red, green and blue spectra. The display system according to claim 11, wherein the retarder generates a phase delay φ for all illumination wavelengths, which has a value in the range of 0.10 to 0.24 for all illumination wavelengths. A method for forming a display system, including: Determining a set of illumination wavelengths, where the set of illumination wavelengths includes at least one illumination wavelength in each of at least three different color spectra; and Select an external retarder with a delay, where the delay is such that: A phase retardation is greater than 0.25 for each of the illumination wavelengths in the group of illumination wavelengths; or A phase retardation is less than 0.25 for each of the illumination wavelengths in the group of illumination wavelengths. The method for forming a display system according to claim 19, comprising orienting a slow axis of the external retarder and a slow axis of a spatial light modulator, wherein: If the phase retardation is greater than 0.25 for each of the illumination wavelengths in the group of illumination wavelengths, the slow axis of the retarder is oriented perpendicular to the slow axis of the spatial light modulator; or If the phase retardation is less than 0.25 for each of the illumination wavelengths in the group of illumination wavelengths, the slow axis of the retarder is oriented parallel to the slow axis of the spatial light modulator. A spatial light modulator system, including: A spatial light modulator includes a first substrate, a second substrate, and a liquid crystal layer located between the first substrate and the second substrate, wherein the spatial light modulator has a spatial light for light propagation Modulator slow axis; and A retarder is located outside the spatial light modulator along an optical path between the spatial light modulator and the retarder, so that the light received by the system is transmitted from the spatial light modulator to the optical path along the optical path The retarder, and wherein the retarder has the characteristics of a retarder phase delay, and wherein the retarder phase delay is greater than 0.25, and wherein the position of the retarder is configured such that the retarder slow axis for light propagation is vertical On the slow axis of the spatial light modulator. The system according to claim 21, further comprising a polarizer arranged along an optical path and having a polarization axis, and wherein the retarder is located between the polarizer and the spatial light modulator, and wherein the retarder is slow The axis is positioned at an angle of 45 degrees with respect to the polarization axis.

Images